The Anodizing of Zirconium and Other Transition Metals in Nitric Acid

Abstract

Zirconium was anodized in solutions of nitric acid and compared with certain other transition metals. At 1 ma/cm2 and concentrations of nitric acid exceeding 14 weight per cent, zirconium was found to develop a low‐resistance oxide layer. Titanium, hafnium, columbium, tantalum, and tungsten showed a high resistance at this current even in 70 weight per cent acid. Hafnium, however, produced a low7hyphen;resistance film at lower current densities. Zirconium, in nitric acid above 14 weight per cent, showed periodic changes of resistance with time. The transition was dependent upon grain orientation and metal texture.